My friend used to have a GoPed that had a hinge underneath it, with an old school shifter lefter that was actually just used to lower/raise the engine. Because of the way the scrubber spins, the tire and scrubber suck each other down toward the ground and give you the friction you're looking for.
I'd try to do something like that if possible, if I had a friction drive setup... but it wouldn't be that important.